Adding algorithms and datastructures

examples/selection_demo.py

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+"""
+Demonstration of selection algorithms.
+
+This script demonstrates the usage of deterministic and randomized selection
+algorithms for finding the k-th smallest element in an array.
+
+Author: Carlos Gutierrez
+Course: MSCS532 - Data Structures and Algorithms
+"""
+
+import sys
+import os
+
+# Add parent directory to path
+sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
+
+from src.deterministic_algorithm import deterministic_select, find_median
+from src.randomized_algorithm import randomized_select, find_median as rand_find_median
+
+
+def demo_basic_selection():
+    """Demonstrate basic selection operations."""
+    print("=" * 60)
+    print("Basic Selection Demo")
+    print("=" * 60)
+    
+    arr = [3, 1, 4, 1, 5, 9, 2, 6, 5, 3, 5]
+    print(f"Array: {arr}")
+    print()
+    
+    # Find various order statistics
+    for k in [1, 3, 5, len(arr)]:
+        det_result = deterministic_select(arr, k)
+        rand_result = randomized_select(arr, k, seed=42)
+        print(f"  {k}-th smallest element:")
+        print(f"    Deterministic: {det_result}")
+        print(f"    Randomized:    {rand_result}")
+        print()
+    
+    # Find median
+    print("Median:")
+    print(f"  Deterministic: {find_median(arr)}")
+    print(f"  Randomized:    {rand_find_median(arr, seed=42)}")
+    print()
+
+
+def demo_different_distributions():
+    """Demonstrate selection on different input distributions."""
+    print("=" * 60)
+    print("Selection on Different Distributions")
+    print("=" * 60)
+    
+    distributions = {
+        "Sorted": list(range(1, 21)),
+        "Reverse Sorted": list(range(20, 0, -1)),
+        "Random": [3, 15, 7, 1, 19, 12, 8, 5, 14, 2, 10, 18, 6, 11, 4, 9, 16, 13, 17, 20],
+        "With Duplicates": [5, 3, 5, 1, 3, 2, 5, 4, 3, 1, 2, 5, 4, 3, 2, 1, 5, 4, 3, 2]
+    }
+    
+    k = 10  # Find 10th smallest
+    
+    for name, arr in distributions.items():
+        print(f"\n{name} Array: {arr[:10]}..." if len(arr) > 10 else f"{name} Array: {arr}")
+        det_result = deterministic_select(arr, k)
+        rand_result = randomized_select(arr, k, seed=42)
+        print(f"  {k}-th smallest:")
+        print(f"    Deterministic: {det_result}")
+        print(f"    Randomized:    {rand_result}")
+    print()
+
+
+def demo_median_finding():
+    """Demonstrate median finding."""
+    print("=" * 60)
+    print("Median Finding Demo")
+    print("=" * 60)
+    
+    test_arrays = [
+        ([1, 2, 3, 4, 5], "Odd length"),
+        ([1, 2, 3, 4, 5, 6], "Even length"),
+        ([5, 2, 8, 1, 9, 3, 7, 4, 6], "Random order"),
+        ([1, 1, 2, 2, 3, 3, 4, 4], "With duplicates")
+    ]
+    
+    for arr, description in test_arrays:
+        print(f"\n{description}: {arr}")
+        det_median = find_median(arr)
+        rand_median = rand_find_median(arr, seed=42)
+        print(f"  Deterministic median: {det_median}")
+        print(f"  Randomized median:    {rand_median}")
+    print()
+
+
+def demo_custom_key():
+    """Demonstrate selection with custom key function."""
+    print("=" * 60)
+    print("Selection with Custom Key Function")
+    print("=" * 60)
+    
+    # Array of dictionaries
+    students = [
+        {'name': 'Alice', 'score': 85},
+        {'name': 'Bob', 'score': 92},
+        {'name': 'Charlie', 'score': 78},
+        {'name': 'Diana', 'score': 95},
+        {'name': 'Eve', 'score': 88}
+    ]
+    
+    print("Students:")
+    for student in students:
+        print(f"  {student['name']}: {student['score']}")
+    print()
+    
+    # Find student with median score
+    median_student = randomized_select(
+        students, 
+        (len(students) + 1) // 2,
+        key=lambda x: x['score'],
+        seed=42
+    )
+    print(f"Student with median score: {median_student['name']} ({median_student['score']})")
+    print()
+
+
+if __name__ == "__main__":
+    print("\n" + "=" * 60)
+    print("Selection Algorithms Demonstration")
+    print("=" * 60 + "\n")
+    
+    demo_basic_selection()
+    demo_different_distributions()
+    demo_median_finding()
+    demo_custom_key()
+    
+    print("=" * 60)
+    print("Demo Complete!")
+    print("=" * 60)
+